PB1993: EXPRESSION OF NEO-201 MAY HELP IN THE DIFFERENTIAL DIAGNOSIS BETWEEN MYELODYSPLASTIC SYNDROMES AND ACUTE MYELOID LEUKEMIA
Authors: Andrea Duminuco, Kwong Tsang, Nunziatina Laura Parrinello, Sara Marino, Loredana Villari, Massimo Fantini, Giuseppe Palumbo, Francesco DI Raimondo, Philip Arlen, Alessandra Romano
Journal: HemaSphere (2023)

Topic: 9. Myelodysplastic syndromes - Biology & Translational Research Background: Acute myeloid leukemia (AML) is a neoplasm of immature myeloid cells associated with a poor prognosis, depending on several intrinsic characteristics (molecular mutations, cytogenetics alterations) or patient-related (age, comorbidities). Myelodysplastic syndrome (MDS) are conditions known to be predisposing, which shares clinical and pathophysiological manifestations with AML. The correct immunophenotyping identification of blast cells rate, fundamental in distinguishing the two pathologies, is necessary. Differential diagnosis between myelodysplastic mature dysplastic neutrophils, promyelocytes, and blasts is currently challenging because of the lack of own markers of dysplastic cells. NEO-201 is an IgG1 monoclonal antibody for the treatment of solid tumors. It derived from an immunogenic preparation of tumor-associated antigens (TAAs) extracted from allogeneic colorectal cancer, targeting core 1 and extended core 1 O-glycans mediating the complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity, expressed by tumor tissue but is not present in healthy epithelial cells. Aims: In this study, the use of NEO-201 in the flow cytometric differential diagnosis between MDS and AML was evaluated. This hypothesis arises from the fact that, following the administration of the antibody to mice, mild neutropenia is observed, which can be explained by the fact that the targeting epitope of NEO-201 core 1 and extended core 1 O-glycans are also expressed on cells of the hematopoietic lineage. Methods: We evaluated by flow cytometry the bone marrow samples of newly diagnosed 21 MDS and 25 AML patients, diagnosed according to the current ELN-working group criteria. The immunophenotypic markers used were CD15, CD45, CD38, CD138, CD14, CD19 and NEO-201. NEO-201 positivity was defined when % of positive cells >10%, and negativity when <10%. Results: NEO-201 is differentially expressed in the bone marrow. CD15+ neutrophil granulocytes are positive for NEO-201 expression, in contrast to monocytes, where it is negative (98.7% [1.4-100] for AML, 98.7 [97.1-100] for MDS). Instead, NEO-201 antigen is absent in blasts and in leukemic cells that are positive for AML markers (e.g., CD34, CD38, CD117). The 27 AML patients reported a median rate of blast cells of 54 and 60% (in morphology and flow cytometry, respectively), with 0% of these cells expressing NEO-201 and 100 [IQR, 100-190] also NEO-201 negative (p<0.05). Rates of total cells NEO-201 positive in BM are 10% [3-32] in AML, and 50% [23-77] in MDS, evidencing the reduction of antigen expression when there is an increase in blast cells. Finally, the median fluorescence intensity evaluated in the two populations on CD15+ cells appear to be superimposable. In figure 1 are reported two samples of bone marrow biopsies, evaluated both with CD34 and NEO-201 antigens, showing the significant presence of NEO-201 in the context of MDS (upper panel), contrary to AML (lower panel), where the presence of blasts is inversely proportional to the expression of NEO-201. Summary/Conclusion: Expression of NEO-201 is not found in blasts, immature cells, and monocytes of the analyzed patients, contrary a CD15+ neutrophil granulocytes where NEO-201 is positive, supporting the proposal to integrate NEO-201 as a marker in the differential diagnosis between AML and MDS and in monitoring the course of patients, leaving open the possibility of use as a future antitumor agent.Keywords: Flow cytometry, Monoclonal antibody, Myelodysplastic syndrome, Acute myeloid leukemia